Long story short, it was a confluence of bad luck and bad advice.
Anyone who watched the Goodwood Festival of Speed last week probably saw Siemens' autonomous Mustang struggle to make its way up the Duke of Richmond's driveway before everything started working correctly. Now, we know why it went wrong.
The Sunday Times took a ride in Siemens' self-driving 1965 Mustang and had a chat with the company about why things went awry early on. It wasn't just one thing, but rather multiple. For starters, the power steering went out (the car is 53 years old, after all), and the system had a hard time compensating for the extra effort required.
Additionally, while the vehicle had radar and lidar sensors, they weren't running at Goodwood, as they were deemed unnecessary. It instead relied upon GPS and a system of "accelerometers and gyroscopes" to cover times when the GPS would have reception issues, like when driving under tree canopies and near Goodwood's famous flint wall.
Furthermore, this car was programmed in a hurry. The Sunday Times reported that a masters student, and not a professor, was in charge of programming the Mustang's software, and it was done in just six weeks.
Apparently, television production only made matters worse. The Sunday Times claimed that the television production crew on hand thought the crowds would want to see the car steering itself around, so the weaving was actually programmed into the drive to make everything seem a bit more dynamic. Shame, that, considering the result made the car look like it wandered out of the pub and not a laboratory. The live television feed equipment installed on the car allegedly interfered with some of the car's systems, too.
So there you have it. Not only was the car not designed to be perfect, the silly whims of television helped contribute to its poor initial outings. As the video below shows, though, things were eventually smoothed out and the car made a successful run up the hill.